I don’t know about you, but I feel that I have a perfectly good perception of reality. Inside my head is a vivid depiction of the world around me, replete with sounds, smells, colour and objects. So it is rather unsettling to discover this might all be a fabrication. Some researchers even contend that the live-stream movie in my head bears no resemblance whatsoever to reality.

“Everybody knows that we don’t see all of reality. I say we see none of it”

On top of this, our brain presents us with only a snapshot. If our senses took in every detail, we would be overwhelmed. Did you notice the last time you blinked, or that fleshy protuberance called your nose that is always in your peripheral vision? No, because your brain edits them out. “A lot of what our senses are doing is something like data compression: simplifying, in order to be able to function,” says Mazviita Chirimuuta at the University of Pittsburgh in Pennsylvania.

In fact, most of what you “see” is an illusion. Our eyes aren’t all-seeing, but capture fleeting glimpses of the outside world between rapid movements called saccades. During these, we are effectively blind because the brain doesn’t process the information that comes in when they happen. If you doubt this, stare into your own eyes in a mirror, then rapidly flick your gaze from one side to the other and back again. Did you see your eyes move?

This is only the start of it. The brain, after all, is sealed in darkness and silence within the solid casing of the skull. It has no direct access to the outside world, and so relies on the information that reaches it via a few electrical cables from our sensory organs. Our eyes pick up information about wavelengths of electromagnetic radiation, our ears detect vibrations of air particles and our noses and mouths detect volatile molecules that we experience as smells and flavours. Through complex processes we only partly understand, the brain integrates these independent inputs into a unified conscious awareness.

The question is, how well does this subjective internal picture represent objective reality?

It is a contentious query, much debated by philosophers and physicists. What do we even mean by objective reality? For Donald Hoffman, a psychologist at the University of California, Irvine, and author of The Case Against Reality, it is “something that exists even if no creature perceives it” (although, ironically, some physicists may beg to differ – see “Do we make reality?”).

But it is impossible to know anything about objective reality without also involving perception and thought. This is why some people think that there is no hard line between objective and subjective reality. “If you have this notion that reality is something that is inherently different from the mind, then it becomes paradoxical to think that we ever have access to reality,” says Chirimuuta. “Reality depends on us, it depends on the way we see the world. But at the same time, what we’re perceiving is one aspect of this reality because our perception is shaped by the senses we happen to have.”

Kind of blue

Take the colour blue. Physicists define it in terms of wavelengths of light, but for Chirimuuta, we can’t remove perception from the equation. Blueness, she argues, isn’t a property of the object but a property of the interaction we have with it.

Other animals probably experience their own versions of reality. This logic also applies to the reality depicted by science. “The world described by physics is also like another interpretation based on measurements taken with scientific instruments that reveal properties and processes that the human senses can’t, by themselves, latch on to,” says Chirimuuta.

Others go further and argue that nothing we perceive bears any resemblance to reality – and that it wouldn’t actually be helpful to “see” things as they really are. “I think that everybody recognises that we don’t see all of reality. I’m saying we see none of reality,” says Hoffman.

To get your head around this, imagine you are playing a virtual reality game. You might be driving a car, for instance, and can see the steering wheel in your hands. “We all know that these objects don’t really exist, they are the result of computer software that renders them,” says Hoffman. There is a reality to the game, but it is the software and circuits of the computer. It would be impossible to play the game if we operated at this level. Instead, our brain perceives constructs such as the steering wheel, letting us play.

Hoffman argues that this trickery doesn’t just happen in video games, but in every moment of our lives. “What I’m claiming is that we’re born with a virtual reality headset on. Evolution gave us a VR headset to simplify things, to give us what we need to play the game of life, without knowing what the reality is.”

According to this view, our brain and sensory system together make a user interface that simplifies the complexity of the world – in the same way that the icons on a smartphone screen are tools to operate the gadget’s underlying circuitry. Everything we see is really an “abstract data structure for something that doesn’t even exist in space and time”, says Hoffman.

This is a dizzying view if you naively think that what you perceive really represents the true nature of the world. But in practical terms, it doesn’t matter. What matters is whether what we perceive allows us to successfully navigate this world – to survive long enough to pass on our genes. “Evolution has shaped us to see things that we have to take seriously, to see what we need to stay alive,” says Hoffman. “But that does not, logically, permit us to say that we’re seeing the truth.” How’s that for a dose of cold, hard reality?